The document discusses Expression Engine (EE), an easy to use content management system (CMS) for professionals. EE is developed by Ellis Lab, who also developed the CodeIgniter framework. EE uses the CodeIgniter framework as its base system starting from version 2.0. Unfortunately, EE requires a commercial license for versions 2.0 and above, unlike its previous free version. However, EE remains a unique and useful CMS despite requiring a commercial license.